Thermally-assisted recording (TAR) patterned-media disk drive with optical detection of write synchronization and servo fields

Abstract

A thermally-assisted recording (TAR) bit-patterned-media (BPM) magnetic recording disk drive uses optical detection of synchronization fields for write synchronization and optical detection of servo sectors for read/write head positioning. The synchronization fields and servo sectors extend generally radially across the data tracks and are patterned into discrete nondata blocks separated by gaps in the along-the-track direction. A near-field transducer (NFT) directs laser radiation to the disk and generates a power absorption profile on the disk that has a characteristic along-the-track spot size less than the along-the-track length of the gaps between the nondata blocks in the synchronization fields and servo sectors. A sensor provides an output signal in response to radiation from the nondata blocks and gaps in the synchronization fields and servo sectors as the disk rotates to control the timing of the magnetic write field applied to the data islands and to control the positioning of the read/write head on the data tracks.

1. A thermal assisted recording (TAR) patterned-media magnetic recording disk drive comprising:
 a rotatable magnetic recording disk having a plurality of concentric data tracks, each data track patterned into discrete magnetizable data islands separated by nonmagnetic spaces, and a plurality of angularly spaced nondata regions extending generally radially across the data tracks, each nondata region patterned into discrete blocks separated by gaps in the along-the-track direction; 
 a write head for applying a magnetic field to the data islands; 
 a laser light source; 
 an optical channel and near-field transducer for directing radiation from the light source to the disk to heat the data islands, the near-field transducer generating a power absorption profile on the disk with a characteristic along-the-track spot size less than the along-the-track length of the gaps between the nondata blocks; 
 a carrier for supporting the write head and near-field transducer, the carrier having a disk-facing surface maintained at a distance less than the wavelength of the laser light from the disk; and 
 a sensor for sensing radiation from the nondata blocks and gaps in the nondata regions as the disk rotates. 
 
     
     
       2. The disk drive of  claim 1  wherein the nondata regions are synchronization fields and the blocks in the synchronization fields are synchronization marks detectable by the radiation sensor for synchronizing the writing of data to the data islands by the write head. 
     
     
       3. The disk drive of  claim 1  wherein the nondata regions are servo sectors and the blocks in the servo sectors are track identification (TID) marks detectable by the radiation sensor for identifying the data tracks by number. 
     
     
       4. The disk drive of  claim 1  wherein the nondata regions are servo sectors and the blocks in the servo sectors are position error signal (PES) marks detectable by the radiation sensor for positioning the write head in the data tracks. 
     
     
       5. The disk drive of  claim 4  wherein the PES marks in the servo sectors are patterned into a null servo pattern disk. 
     
     
       6. The disk drive of  claim 1  further comprising a write clock responsive to said sensor and coupled to the write head for controlling the timing of the magnetic field applied to the data islands by the write head. 
     
     
       7. The disk drive of  claim 1  further comprising servo electronics responsive to said sensor for controlling the positioning of the write head on the data tracks. 
     
     
       8. The disk drive of  claim 1  wherein the nondata blocks comprise metallic or metallic alloy material and the gaps between the blocks comprise non-metallic material. 
     
     
       9. The disk drive of  claim 1  wherein the disk has a surface topography with regions of peaks and regions of valleys, and wherein the nondata blocks are peaks and the gaps between the blocks are valleys. 
     
     
       10. The disk drive of  claim 1  wherein the magnetizable data islands are magnetizable substantially perpendicular to the plane of the disk. 
     
     
       11. The disk drive of  claim 1  wherein the radiation sensor is responsive to radiation reflected from the near-field transducer through the optical channel. 
     
     
       12. The disk drive of  claim 11  wherein the radiation sensor comprises a photodetector. 
     
     
       13. The disk drive of  claim 1  wherein the near-field transducer has a primary tip at said disk-facing surface for heating the islands as the disk rotates and a secondary tip spaced from the primary tip, and wherein said radiation sensor comprises an electrical conductor on the carrier near the secondary tip, the electrical conductor being heated by the secondary tip and exhibiting a change in electrical resistance in response to a change in temperature, and electrical circuitry coupled to the electrical conductor and providing an output signal representative of change in electrical resistance of the sensor. 
     
     
       14. A thermal assisted recording (TAR) patterned-media magnetic recording disk drive comprising:
 a rotatable magnetic recording disk having a plurality of concentric data tracks, each data track patterned into discrete magnetizable data islands separated by nonmagnetic spaces, and a plurality of angularly spaced nondata synchronization fields extending generally radially across the data tracks, each nondata synchronization field patterned into discrete nondata blocks separated by gaps in the along-the-track direction; 
 a write head for applying a magnetic field to the data islands; 
 a laser light source; 
 an optical channel and near-field transducer for directing radiation from the light source to the disk to heat the data islands, the near-field transducer generating a power absorption profile on the disk with a characteristic along-the-track spot size less than the along-the-track length of the gaps between the nondata blocks; 
 a carrier for supporting the write head and near-field transducer, the carrier having a disk-facing surface maintained at a distance less than the wavelength of the laser light from the disk; 
 a sensor providing an output signal in response to radiation from the nondata blocks and gaps in the synchronization fields as the disk rotates; and 
 a write clock responsive to said sensor output signal and coupled to the write head for controlling the timing of the magnetic field applied to the data islands by the write head. 
 
     
     
       15. The disk drive of  claim 14  wherein the nondata blocks comprise metallic or metallic alloy material and the gaps between the blocks comprise non-metallic material. 
     
     
       16. The disk drive of  claim 14  wherein the disk has a surface topography with regions of peaks and regions of valleys, and wherein the nondata blocks are peaks and the gaps between the blocks are valleys. 
     
     
       17. The disk drive of  claim 14  wherein the radiation sensor is responsive to radiation reflected from the near-field transducer through the optical channel. 
     
     
       18. The disk drive of  claim 14  wherein the near-field transducer has a primary tip at said disk-facing surface for heating the islands as the disk rotates and a secondary tip spaced from the primary tip, and wherein said radiation sensor comprises an electrical conductor on the carrier near the secondary tip, the electrical conductor being heated by the secondary tip and exhibiting a change in electrical resistance in response to a change in temperature, and electrical circuitry coupled to the electrical conductor and providing an output signal representative of change in electrical resistance of the sensor. 
     
     
       19. A thermal assisted recording (TAR) patterned-media magnetic recording disk drive comprising:
 a rotatable magnetic recording disk having a plurality of concentric data tracks, each data track patterned into discrete magnetizable data islands separated by nonmagnetic spaces, and a plurality of angularly spaced nondata servo sectors extending generally radially across the data tracks, each nondata servo sector patterned into discrete nondata servo blocks separated by gaps in the along-the-track direction; 
 a write head for applying a magnetic field to the data islands; 
 a laser; 
 an optical channel and near-field transducer for directing radiation from the laser to the disk to heat the data islands, the near-field transducer generating a power absorption profile on the disk with a characteristic along-the-track spot size less than the along-the-track length of the gaps between the nondata servo blocks; 
 a carrier for supporting the write head and near-field transducer, the carrier having a disk-facing surface maintained at a distance less than the wavelength of the laser light from the disk; 
 a sensor providing an output signal in response to radiation from the nondata servo blocks and gaps in the servo sectors as the disk rotates; and 
 servo electronics responsive to said sensor output signal for controlling the positioning of the write head on the data tracks. 
 
     
     
       20. The disk drive of  claim 19  wherein the laser is capable of providing a write power output for heating the data islands in the presence of the magnetic field from the write head and a lower power output less than the write power output, and further comprising a read head on the carrier for reading of data from the data islands, and wherein the laser is at said lower power output during reading. 
     
     
       21. The disk drive of  claim 19  wherein the nondata servo blocks are track identification (TID) marks detectable by the radiation sensor for identifying the data tracks by number. 
     
     
       22. The disk drive of  claim 19  wherein the nondata servo blocks are position error signal (PES) marks detectable by the radiation sensor for positioning the write head in the data tracks. 
     
     
       23. The disk drive of  claim 19  wherein the nondata servo blocks comprise metallic or metallic alloy material and the gaps between the blocks comprise non-metallic material. 
     
     
       24. The disk drive of  claim 19  wherein the disk has a surface topography with regions of peaks and regions of valleys, and wherein the nondata servo blocks are peaks and the gaps between the blocks are valleys. 
     
     
       25. The disk drive of  claim 19  wherein the radiation sensor is responsive to radiation reflected from the near-field transducer through the optical channel. 
     
     
       26. The disk drive of  claim 19  wherein the near-field transducer has a primary tip at said disk-facing surface for heating the islands as the disk rotates and a secondary tip spaced from the primary tip, and wherein said radiation sensor comprises an electrical conductor on the carrier near the secondary tip, the electrical conductor being heated by the secondary tip and exhibiting a change in electrical resistance in response to a change in temperature, and electrical circuitry coupled to the electrical conductor and providing an output signal representative of change in electrical resistance of the sensor.